In general, a boom floating function means a function in which a bucket moves up and down along an uneven surface of the ground only by the self weight of a boom even if an operator performs boom-down operation during working. That is, in the case where an arm is operated in forward and backward directions and the boom-down operation is performed, a bucket surface moves along the uneven surface of the ground without cutting the uneven surface through the floating function.
Through this, if a floating mode is selected by an operator depending on a work type, ground leveling work can be performed in a state where hydraulic fluid is not supplied from a hydraulic pump, whereas if a normal excavating work mode is selected, the floating mode is released and the hydraulic fluid is supplied from the hydraulic pump to perform the corresponding work. In the case of performing the ground leveling work through switching to the floating mode, the hydraulic fluid of the hydraulic pump is not used, and thus work efficiency and productivity can be heightened.
On the other hand, in the case of switching to the floating mode, it is not possible to perform a work to scrape down a wall surface by the bucket or a jack-up work to lift a body of the equipment (lower driving structure and upper swing structure) in a state where the bucket comes in contact with the ground, and thus it is required for the operator to switch the equipment to a normal work mode to cause inconvenience in use.
FIG. 1 is a graph explaining a discharge flow rate of a hydraulic pump in the case where an excavator is switched to a floating mode in the related art. In the case where the present mode is switched to a floating mode in which ground leveling work for smoothing the ground can be performed without supplying hydraulic fluid from a hydraulic pump to a hydraulic cylinder, the flow rate is calculated only through an operation of an arm (see curve “b” in the graph) even if there is a boom-down operation signal (see curve “a” in the graph), and thus the discharge amount of the hydraulic pump is reduced (see curve “c” in the graph) if a time when the operation amount of the arm is reduced arrives.